Abstract
In this study, the effect of the parameters playing a role in the root flow behavior of HAWT are only partly understood. To better reveal the root flow properties, this study presents the progression of HAWT blade root flow at two different blade geometries and at two different tip speed ratios. The effects of the geometry and the tip speed ratio on the root flow behavior and on the evolution of the root flow features are investigated. This study aims to answer the following questions: (i) What are the effects of the blade geometry and tip speed ratio on the root flow behavior? (ii) How are the blade wake and the root vortex evolution affected by the change of these parameters? The analysis of the velocity fields shows that the radial flow behavior changes with different blade geometries but a remarkable difference in the radial flow behavior is not observed with the change of tip speed ratio. The formation of the wake is different at three test cases because of different loading that the blades are encountered. From the circulation distribution along the blades, while a strong root vortex can be observed in Blade 1, the bound vorticity along Blade 2 builds up gradually when moving outboard, and do not show a trace of a strong root vortex.
Highlights
The horizontal axis wind turbine (HAWT) wake has widely been investigated and reported in literature
To better reveal the root flow properties, this study presents the progression of HAWT blade root flow at two different blade geometries and at two different tip speed ratios
This study aims to answer the following questions: (i) What are the effects of the blade geometry and tip speed ratio on the root flow behavior? (ii) How are the blade wake and the root vortex evolution affected by the change of these parameters? The analysis of the velocity fields shows that the radial flow behavior changes with different blade geometries but a remarkable difference in the radial flow behavior is not observed with the change of tip speed ratio
Summary
The horizontal axis wind turbine (HAWT) wake has widely been investigated and reported in literature. Among the near wake studies, the outboard region of the blade has taken the most of the attention; there has been limited research in the near wake of the root region. This may be because of two main reasons: (i) the power production from the root region is less significant important compared to the outboard region and (ii) the difficulties of both measurements and advanced calculations in the root region. The hub vortex analysis by Ebert and Wood [2] suggested that the hub vortices merging into a single hub vortex along the axis of rotation, opposing the experiments of Whale et al [3], which showed the hub vortices merging with the tip vortex system. Whale et al [3] were among
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